Welding wires commonly used for GMAW (Gas Metal Arc Welding) and SAW (Submerged Arc Welding) typically carry a copper metal coating (cladding) to reduce friction and electrical resistance between the welding wire and the welding gun's contact tip through which the welding wire passes. In contrast, FCAW (Flux-Cored Arc Welding) welding wires typically carry a wire feeding lubricant comprising a solid lubricant such as MoS2, WS2, graphite and/or PTFE (Teflon) for this purpose. A binder such as vegetable oil, mineral oil, synthetic oil or petroleum wax is included in the wire feeding lubricant for adhesion purposes and to enhance feedability, i.e., the ease of withdrawing the wire from its supply container and feeding the wire through the contact tip without tangling. Arc stabilizers, which are typically sodium or potassium containing soaps or detergents, etc., can also be dissolved and/or dispersed in the binder. See, for example, Kokai (Japanese Published Unexamined Application) 2004-034131, Kokai 08-257788, Kokai 2002-219595, Kokai 2002-239779, U.S. Pat. No. 6,337,144 and Kokai 2003-039191, the disclosures of which are incorporated herein by reference.
In accordance with this invention, the electrical resistance between a welding wire and the welding gun's contact tip is substantially reduced by providing on the welding wire's surface a thermally stable, electrically conductive solid in fine particulate form. The result, it is believed, is that arc stability will be improved and the useful life of the contact tip will be increased.
Thus, this invention in its broader aspects provides a welding wire for use in arc welding comprising a welding wire substrate and a solid conductor on the surfaces of the welding wire substrate, the solid conductor comprising a thermally stable, electrically conductive particulate solid.
In a particular embodiment, this invention provides a welding wire comprising a welding wire substrate and a wire coating on the outside surfaces of the welding wire substrate, the wire coating comprising a solid lubricant, a solid conductor comprising a thermally stable, electrically conductive particulate solid, and a binder.
In addition, this invention also provides an improved welding wire coating comprising a solid lubricant, a solid conductor comprising a thermally stable, electrically conductive particulate solid, and a binder.